It is desirable to provide a tile product having the appearance of solid natural stone such as marble, but without the disadvantages of solid stone. Natural stone such as marble is often used as a floor or wall covering tile. A single piece or slab of natural stone such as marble is generally cut and finished to form a tile of desired size and shape. However, due to the high density of natural stones such as marble, tiles of acceptable thickness are very heavy. Thinner tiles, on the other hand, have limited strength and tend to shatter or break.
Conventional natural stone tile, e.g., marble, is very difficult to install, and installation is generally accomplished by an experienced "marble man," i.e., installation of marble is generally not thought of as a "do-it-yourself" project.
One of the most difficult aspects of natural stone, e.g., marble, installation is the selection of an appropriate mortar mix to adhere the stone to the, e.g., wall or floor. Marble mortar mix is fundamentally composed of mortar and sand. However, different pieces of natural stone require different mixes. The mix is chosen primarily based on the density of the stone which "marble men" learn to judge by feel, touch, sound, sight and even taste. "Marble men" routinely exchange information regarding techniques and variations for mixing mortar, sand and other components to make various mortar mixes. The selection and mixing of mortar mixes can be thought of more as an art than a science. Additives are mixed with mortar and sand, such as perlite which adds body to the mix to give it more "stand-up" ability. The additives are also chosen for their sound insulation qualities. As a consequence of the knowledge required to lay natural stone tiles, the installation costs on a square foot basis are high and, further, there is a limited supply of skilled masons who are available to install natural stone tiles.
Conventional natural stone tiles must be installed by "floating" the tiles on the mortar mix; that is, the back surface of the tile is not brought into contact with the surface on which it is being installed. Thus, a further difficulty in installing conventional natural stone tiles resides in the need to use a mortar mix having the correct thickness and viscosity to float the stone tiles so that the upper surfaces of all the installed tiles are level. Thickness variations within each tile and between a plurality of tiles further complicate installation. These thickness variations are due to the fact that the major surfaces of the stone slabs which are ground and polished to form tiles are not flat. Thus, there is no flat surface to serve as a datum plane during the grinding and polishing operations.
The problem of selection and mixing of appropriate adhesives is particularly acute when the installation design requires use of multiple colors of stone, multiple types of stone or both multiple colors and multiple types of stone. For example, as shown in FIG. 1, an installation design may require use of more than one type of natural stone tile. For example, two types of natural stone tile designated A and B may be required. The types A and B may differ in color or may differ in the type of natural stone, e.g., type A may be marble and type B may be slate. Using conventional natural stone tiles, a different mortar mix may preferably be used for type A than would be used for type B. Differences in density even among type A tiles or among type B tiles may require selection and use of different mortar mixes. These factors contribute to the difficulty of installing conventional natural stone tiles.
The installation of ceramic tiles is conventionally accomplished with mastics which are purchased in pre-mixed containers. The mastic has a standard viscosity which is easily worked with tools designed for ceramic tile installation. Furthermore, the ceramic tiles typically have protrusions to establish a uniform adhesive thickness and height with respect to the surface on which the ceramic tile is being installed. Unlike the installation of natural stone with mortar mixes, the installation of ceramic tile may be performed with less skilled labor including substantial installation on a "do-it-yourself" basis.
U.S. Pat. No. 3,878,030 to Cook states that the prior art has suggested solving some of the problems associated with natural stone, particularly with marble, by bonding a plurality of small pieces having the desired texture and thickness to an underlying piece of the same material. The underlying piece is then chosen from stone strata which does not have the desired texture and which is therefor less expensive. In this manner, the more expensive desirable pieces can be cut thin so as to increase their economic utilization and are bonded to a generally thicker layer of less valuable stone. However, it is disclosed that the bonding of stone to stone still produces a relatively thick and quite heavy structure. It is also disclosed that such stone-to-stone structures are brittle and require considerable care in finishing, handling, storage and installation. Cook proposes providing a piece of wood product, such as a fiberboard, as an underlayment, then applying a bonding material, preferably a two-part curable cement, to the under-layment and/or to one surface of a plurality of discrete pieces of relatively thin stone. The stone pieces are then placed on the top of the underlayment and the cement is allowed to cure to firmly bond the pieces to the underlayment. Thereafter, the bonded-together structure is subjected to a finishing operation including a grinding operation while being subjected to a water bath and then to a polishing operation such as the use of a felt polishing wheel in connection with a tin oxide slurry or powder.
U.S. Pat. No. 3,097,080 to Weir discloses an artificial stone facing plaque which comprises essentially a thin body with a decorative upper or forward face, and composed of a settable synthetic organic plastic material in which are embedded, at least partially, a plurality of pieces of relatively coarse aggregate. If desired, the plastic plaque may be bonded to a suitable backing strip which may be formed of any suitable material such as, for example, asbestos cement board. It is often desirable to have the top portion of the individual aggregate partially ground off to form the polished surfaces. In some instances, it is also desirable to have the exposed forward or top decorative face of the plaque smooth and polished. In such instances, the protruding portions of the aggregate and also a portion of the plastic face or surface are ground away so that the final exposed surface of the plaque is slightly below that of the original forward surface of the plastic body.
U.S. Pat. No. 4,621,001 to Bard discloses a tile-shaped composite element in which a ceramic tile serving as the visible tile is glued to a further ceramic tile serving as the base tile. Each tile is provided on the back with a nesting structure and glued together with this nesting structure back-to-back. Since the wall thickness of such a composite element may correspond to the usual wall thickness of shingles of conventional ceramic tiles, extremely thin tiles may be used as the base tile and the visible tile placed thereupon.
U.S. Pat. No. 4,640,850 to Marocco discloses a composite facing slab which comprises a sheet of natural stone, such as marble, and a protective layer constituted by a sheet of transparent glass. The latter is fixed to the face of the stone sheet intended to remain visible with the interpositioning of an interlayer of transparent thermoplastic material which can adhere to both the sheets and fills the surface defects of the stone sheet.
U.S. Pat. No. 4,664,955 to Clem discloses a composite laminate for use in paneling of walls, ceilings and other surfaces such as furniture and the like. The composite laminate comprises a polymeric sheet-like core having a pair of surfaces to which are bonded a metal foil so as to form a sandwich-type structure and wherein a lamina of natural facing stone is uniformly bonded to at least one of the pair of metal foils.
U.S. Pat. No. 4,036,929 to Gould discloses a method of forming decorative inserts in granite and the like. A cavity is cut or sandblasted in the stone to produce a decorative design. An epoxy resin base is inserted into the cavity and permitted to set. Decorative glass chips are arranged in a mosaic-like pattern in a resin of similar properties to the base and the mortar, and a bond is formed between the base resin, the mortar resin and the decorative chips to provide a pattern on the stone.
A product known as "GL Marble" manufactured by Technomaiera, S.p.A, is a natural marble sliced into thin sheets 1/4" thick, reinforced with a coating of epoxy and glass fibers, and cut into standard sizes 1.times.2, 2.times.2 and 2.times.4. Marble Technics, Ltd., of New York, a distributor of this product, describes "ISO Marble" as an extension of the GL Marble technology wherein full size sheets of GL Marble are laminated as a facing of a sandwich panel whose core is a non-combustible vermiculite board with a backing of 1 mm bonderized steel. These types of products have the disadvantage that the thermal expansion coefficients of the marble and fiberglass backing are not matched.
Therefore, it is still desired to provide a tile product the appearance of which is equivalent to ordinary marble slab, but is lighter in weight and higher in strength than ordinary marble and presently available marble products.